Fire and smoke inhalation cause many deaths in otherwise survivable aircraft accidents. Investigations indicate that fires usually are caused when the highly volatile fuel spills from damaged tanks and splatters throughout the wreckage. Fuel vaporizes and is easily ignited by hot engine parts or sparks from metal impact. Preliminary studies have demonstrated that gelled fuels are less likely to explode or burst into flames under aircraft crash conditions, and thus gelled fuels are a safety factor in jet aircraft.
In application Ser. No. 222,600, now U.S. Pat. No. 3824085, assignee of the present invention, there is disclosed a cellulose derivative and a set of processing conditions to product gelled or thickened jet fuel. Gelation or thickening is achieved by the fact that particles of dissolved polymers of carbohydrate derivatives can agglomerate to form a coherent structure and trap the fuel within the gel matrix. The gelling agent referred to in application Ser. No. 222,660 is hydroxypropyl cellulose laurate with a degree of molecular substitution of hydroxypropyl groups of 2 to 6, preferably 3 to 4, and a degree of substitution of laurate groups of 2 to 3.
Although the product and process of said application are quite satisfactory, it would be a substantial improvement if the viscosity of the gelled jet fuel could be increased without an increase in the total solid content of the gel. The process of the present invention increases the viscosity of the fuel gel of U.S. application Ser. No. 222,660 using hydroxypropyl cellulose laurate as the gelling agent one hundred fold.
Thus, one of the principal objects of the present invention is to provide a hydrocarbon or nonpolar solvent gelled or thickened with a lipophilic polymer carbohydrate derivative and synergistic additive. Another principal object of this invention is to provide a gelled jet fuel having incorporated therein hydroxypropyl cellulose laurate and a synergistic additive to provide for an unexpectedly high viscosity.